1. Field of the Invention
This invention relates to a charging apparatus for an electric vehicle, and more particularly to a charging apparatus for an electric vehicle which can prevent terminals in a charging coupling from becoming overheated and melting.
2. Statement of the Prior Art
Electric vehicles will find increasing use in the near future in view of environment and energy. As such, the problem of battery charging must be overcome. In particular, a coupling for charging raises an important problem. A charging coupling includes a vehicle inlet or a vehicle connector installed in an electric vehicle and a supply connector or a power source connector connected to a power source on the ground. The vehicle inlet and supply connector have supply terminals which conduct a charging current and signal terminals which control the charging current. Charging work is carried out under relatively high voltages of 200 to 500 V and relatively high currents of 80 to 150 A. Accordingly, an arc is prevented from occurring between the supply terminals upon fitting the charging coupling.
It is effective in charging coupling to extend the supply terminals and to shorten the signal terminals so that the signal terminals are contacted with each other after the supply terminals have been contacted with each other and the supply terminals are enabled to conduct a charging current after contacting of the signal terminals upon fitting the coupling and so that the supply terminals are inhibited to conduct the current after separating of the signal terminals upon detaching the coupling. That is, a difference between lengths of the supply terminals and signal terminals causes a difference between mechanical contact times of respective terminals upon fitting and detaching in coupling.
In actual charging work, an operator holds the supply connector and pushes it into or pulls it out from the vehicle inlet. In the case of fitting and detaching the charging coupling there is no problem so long as the supply connector is driven rapidly and straight during insertion and extraction.
However, if the supply connector is not aligned properly, the signal terminals chatter, that is, they repeatedly contact with and separate from each other, at the commencement of contact or when detachment is terminated. Then, since the supply terminals contact each other under a state of incomplete fitting, chattering of the signal terminals cause the charging circuit to open and close so as to conduct and shut off the charging current, thereby overheating and possibly melting the supply terminals.
In order to avoid such a problem, it is possible to prevent chattering by increasing the difference between the lengths of the supply terminals and signal terminals to thereby extend the interval between the contacting and separating times. However, in this case, the coupling will be large in size and inconvenient to handle.